- keywords:
    - add some limits to how many there can be
       - don't return \* in PERMANENTFLAGS when we're full
    - remove unused keywords?

 - caching
    - force bits should be used only for nonregistered fields
    - change envelope parsing not to use get_headers() so imap.envelope can
      actually be cached without all the headers..
    - compression should drop fields with last_used <
      (latest_mail_index_date - month)
    - we could try compressing same field values into a single
      location in cache file.
    - support caching all message headers. this could be useful when
      indexes are in local disk but actual mails are accessed through NFS.

 - mbox
    - dirty state should be stored to index (with mbox_very_dirty_syncs)
    - after some locking timeouts: mbox-lock.c: line 518 (mbox_lock):
      assertion failed: (lock_type == F_RDLCK || mbox->mbox_lock_type != F_RDLCK)
    - controldir for mboxes too and place subscriptions file there?
    - size.physical isn't cached, but should it even be? ..
    - syncing existing indexes takes 4x longer than creating new one, why?
    - how well does dirty sync + status work? it reads the last mail every
      time? not very good..
    - always add empty line. make the parser require it too? syncing should
      make sure there always exists two LFs at end of file. raw-mbox-stream
      should make sure the last message ends with LF even if it doesn't exist
      in the file
    - Quote "From ", unquote ">From "
    - COPY doesn't work to itself (lock assert crash, for now just disallowed)
    - keep mbox lock for two extra seconds after sync (do we really need to?)
    - move /var/mail/user to ~/mbox if ~/mbox exists.. supposedly this
      could be useful if /var/mail doesn't have quota, but ~/mail does.
      now, what do we then do if we can move only some of the mails?..
    - if we can't create dotlock file for mbox, make sure it still can be
      selected in read-only state

 - maildir
    - if indexes exist but dovecot-uidlist doesn't, it's not tried to be
      recreated
    - with pop3 don't move messages from new/ to cur/ before RETR
    - when sorting maildir files, sort based on Mxxxx first so the files are
      sorted always in ascending order. required for proper out-of-quota
      uidlist handling

 - dbox
   - keyword list header locking isn't correct now. saving uses file's
     dotlock, sync uses sync lock. and what about reading?...
   - dbox is leaking index fds
   - append_offset in header shouldn't be trusted
   - show in index if there are expunge-flagged mails in the mailbox
   - pop3_lock_session doesn't work

 - index
    - dd if=/dev/zero of=dovecot.index bs=1024 count=1 -> NOOP -> crash!
    - delete >30min old dovecot.index.log.2 files when opening index?
    - Panic: file mail-index.c: line 844 (mail_index_sync_from_transactions):
      assertion failed: (hdr.messages_count == (*map)->hdr.messages_count)
    - Corrupted transaction log file dovecot.index.log: record size wrong (type 0x4, 20 % 12 != 0)
      -> mail-index.c: line 841 (mail_index_sync_from_transactions): assertion failed: (hdr.messages_count == (*map)->hdr.messages_count)
    - optimize initial left_idx in _view_lookup_uid_range()
    - if log file is lost, generate it from old and new index
    - transaction log: when replacing log with a same sequence, we remove it
      from log's file list, but we don't do anything to existing log views.
      this can crash later in mail_transaction_log_view_set() because 'first'
      is from log list, while we're comparing it into view->tail which it never
      is. also overwriting it leaks memory..
    - read-only support for mailboxes where we don't have write-access

 - namespaces
    - namespaces: add new "auto_disable" flag so if the mailbox can't be opened
      (eg. file doesn't exist), just ignore the problem and disable the
      namespace
    - subscribe <namespace prefix> doesn't work.
    - namespaces don't work in plugins: acl, trash, convert
    - subscriptions file should contain namespace prefixes. at least optionally.
      there's the subscriptions = yes setting now for namespaces.. do it so that
      if prefix = "" has subscriptions, it contains prefixes. otherwise not.
       - for shared/public namespaces default to "no"

 - lib-storage
    - calls fsync()s etc. less often (when copying). optionally disable them.
    - x search charset asdf all -> should fail
    - index_removal_timeout gets leaked in some conditions. how?
    - subscribe: IMAP(anonymous): open(anonymous/mail/.temp...) failed: Permission denied
    - should we allow following symlinks in mbox/maildirs? they are now.
       - if we implement shared mailboxes with shared indexes, never do that or
	 others could symlink your personal mailboxes and see the indexes
	 created for it which may contain envelope etc. data
       - this allows circular mailbox hierarchies which should be prevented by
	 eg. allowing max. 20 hierarchies.

 - login
    - when pipelining login command + post-login commands, login process should
      pass the command to imap/pop3 process (at least one pop3 client does this)
    - imap-login: Master sent reply with unknown tag 1. client closed
      connection at the exact same time master was logging it in?
      see master_request_abort()
    - Digest-MD5: support integrity protection, and maybe crypting. Do it
      through login process like SSL is done?
    -  x login foo bar
       x NO Authentication failed.
       x login cras pass
       * BYE Disconnected for inactivity.
	^ but it's not disconnecting! (buggy dovecot-auth not replying)
	  probably because userdb lookup didn't reply, and fd was already sent
	  for master.. should imap-login be handling it anymore?..
    - imap-login: Authenticate PLAIN failed: Authentication failed:
      Authentication server isn't connected, try again later.. [127.0.0.1]
        ^ NO Authentication failed. (should be Temporary login failure!)
    - if auth process dies, login process should retry authentication if
      possible. or if not, disconnect the client so it doesn't think the auth
      failed.
    - send client IP immediately after accept() to master process. make sure
      master shows the IP if login dies unexpectedly. master should probably
      also kill the login process if it doesn't kill itself soon enough.. or
      maybe just log the IP immediately.

 - auth
    - ability to specify default password scheme with passwd-file
    - with blocking passdb we're not caching lookups if the password was wrong
    - if PAM child process doesn't finish within a minute, kill it
    - PAM / checkpassword should use passdb-blocking
    - support specifying hex/base64 encoding in password scheme. for example
      {plain-md5.base64}
    - auth cache: cache userdb data too.
    - remove system_user and allow returning multiple gids instead.
    - SIGHUP restarts auth processes .. but does it wait until they've finished
      with all requests? no.
    - post-login-sql-command (userdb command doesn't do because of deliver)
    - does dovecot-auth really break when it runs out of fds?
    - dovecot-auth should limit how fast authentication requests are allowed
      from login processes. especially if there's one login/connection the speed
      should be something like once/sec. also limit how fast to accept new
      connections.
    - support read-only logins. user could with alternative password get only
      read-access to mails so mails could be read relatively safely with
      untrusted computers. Maybe always send [ALERT] about the previous
      read-only login time with IP?
    - dovecot-auth workers: create a separate dovecot-pam worker which shares
      pretty much all code with dovecot-auth worker but isn't linked against
      any libraries. or..? this might be difficult to do, especially because the
      workers currently can handle any kind of passdb/userb requests. perhaps
      there should be a completely separate simple PAM authenticator binary.

 - master
    - Support listening in multiple sockets
    - per-user/ip limits..
    - configurable syslog prefix
    - SIGHUP rather shouldn't restart listening sockets if they didn't change..
    - if there are duplicate settings, complain about it

 - quota
    - if dovecot-uidlist can't be written, assume the new mails have UIDs 
      beginning from uidlist.next_uid. Whenever mails are expunged, overwrite
      the next_uid field with the current highest next_uid. Whenever we have
      assumed UIDs and uidlist gets updated, throw the client out with
      "inconsist mailbox".
    - make sure all syscalls check for ENOSPACE (and ENOACCESS while at it)
    - quota code should probably be always doing some quota_set_critical()
      instead of using mail_storage_set_critical(), so that quota_last_error()
      would work properly
    - if storage=0 is given, use unlimited quota but track it anyway

 - ssl
    - add setting: ssl_options = bitmask. by default we enable all openssl
      workarounds, this could be used to disable some of them
    - gnutls support isn't working

 - search
    - message header search: we should ignore LWSP between two MIME blocks
    - message_body_search() could accept multiple search keywords so we
      wouldn't need to call it separately for each one (so we wouldn't need
      to parse the message multiple times).
    - message_body_search() could support NULL MessagePart and the searching
      could be done while parsing the message. this would need changes to
      message_parse() as well.
    - could optionally support scanning inside file attachments and use
      plugins to extract text out of them (word, excel, pdf, etc. etc.)
    - use a trie index for fast text searching, like cyrus squat?
    - Create our own extension: When searching with TEXT/BODY, return
      the message text surrounding the keywords just like web search engines
      do. like: SEARCH X-PRINT-MATCHES TEXT "hello" -> * SEARCH 1 "He said:
      Hello world!" 2 "Hello, I'm ...". This would be especially useful with
      the above attachment scanning.

 - lib-charset
     - utf8_toupper() is a must. and a bit difficult if we want to do it right.
     - add support for other things than iconv() as well? we could reuse
       the code from cyrus or courier
     - cache iconvs? they'd probably be faster if we just reset the
       conversion instead of opening new one every time. and there will likely
       be only one or two charsets which are used for nearly all conversions.

 - deliver
    - empty mail gives an error.
    - We should always return EX_* failures and never our own 89 etc.

 - general
    - add imap_logout_format
    - stop using atol(), atoi(), strtoul() etc. in places where we actually
      care about what they return, and rather create our own function which
      checks if the input overflows the integer, and if so call i_fatal()
    - solaris sendfile is broken?
    - rfc2231 continuation support (useless?)
    - rfc2557 support for BODYSTRUCTURE, as specified by RFC3501
    - LMTP server
    - ability to build plugins statically into the binaries
    - ~/.dovecotrc to override system wide settings. namespace settings should
      override all the previous namespace settings instead of adding new.
    - option to disable SORT, SEARCH and other memory/cpu-intensive features.
      defaults and per-user by dovecot-auth.
    - dotlock overriding is racy, but it's pretty difficult to fix it. Also
      overriding someone else's dotlock in shared folder isn't possible. These
      could be fixed by having separate lock process running as root, which
      would chown() the file for another uid and then unlink() it as that user.
      One problem with that is that if malicious user sets setuid+execute bits
      on for the file, he could run the file and get changed to the new uid.
      That hopefully shouldn't matter much since the new uid should be user
      with minimum possible privileges. Anyway, optional..
    - things break if next_uid gets to 2^32

capabilities:
 - preferrably all should be implemented as plugins
 - possibility to disable them from config file
 - THREAD=ORDEREDSUBJECT - although pretty useless I'd think.
 - acl (rfc2086, draft-ietf-imapext-acl), namespace (rfc2342)
     - probably do it like cyrus. "user.<username>" to access other
       users, with "" defaulting to "user.<myself>". these should be
       configurable however.
     - shared namespaces? maybe configurable in config file
     - easiest way to do ACL would be to use unix modes, but is that
       useful at all? Well, ACL2 has a bit better support for that, so
       maybe we could support it.
     - otherwise gets a bit trickly, we could keep all mail in "imapmail"
       group and 0600/0700 mode by default, but when mail is shared to others,
       the group read/write access bits would be set. or alternatively we
       could launch another imap process to handle it, which we should support
       anyway. ACLs could be stored into ".acl" ascii file in each folder.
     - support for private and shared flags, configurable by mailbox admin.
       this isn't in any draft yet, but ACL2 author was going to create one.
       [SHAREDFLAGS (...)] would specify which ones are shared, don't know yet
       how they would be configured.
 - id (rfc2971)
     - must be configurable what gets sent, default to only name=Dovecot
     - separate pre/post-login settings
     - optionally log configured parts of the client information, but only
       once, probably at the same time as logging "Logged in",
       "Disconnected", etc.
     - remember to force truncating values longer than 30 chars,
       especially before logging
 - mailbox-referrals (rfc2193)
     - this is useful whenever we would otherwise need to make the
       connection ourself. for example load balancing and shared mailboxes
       requiring another UID to run.
     - this rfc defines no exact way for server to detect if client
       supports referrals or not. I don't think there's much point in
       supporting only referrals, as most clients don't support them.
       Instead we should return referrals when we know that client
       supports them, otherwise do the connecting ourself. If client
       issues RLIST or RLSUB command, it's safe to assume it supports
       referrals.
     - for load balancing this works just fine, but what about shared
       mailboxes which require different UID? If we login with our own
       username, we end up with our own UID instead of what we wanted.
       IMAP URLs don't support separated authorization id which would
       have made this very easy.. We could give the "userid@group" as
       userid, but clients probably treat it as different userid and
       ask the password again.
     - problems, problems, .. maybe not worth the trouble.
 - drafts:
     - http://www.imc.org/ids.html
     - annotate (draft-ietf-imapext-annotate)
	 - per-message annotations. this will be major change. especially
	   because currently there's no suitable storage for them, and
	   they'll probably change all the time.. maybe if we moved into
	   berkeley db to store the .data file and these annotations.
	 - this is separate problem from index files. indexes are treated as
	   temporary files, annotations are permanent data. we'd have to
	   support non-db way to do this too, which would probably be just a
	   simple (slow) text file.
     - annotatemore (draft-daboo-imap-annotatemore)
	 - server and per-mailbox annotations. much easier than
	   per-message annotations, but they'd be easier to place into
	   db as well.
     - binary (draft-nerenberg-imap-binary)
	 - perhaps not too useful. I'd like to make Dovecot fully
	   binary-safe though.
     - view (draft-ietf-imapext-view)
         - slow, complex, luckily draft expired almost two years ago.
	   i hope i don't have to implement this :)
	 - can be done client-side just fine (evolution's virtual folders)